A reduction in a heart's cardiac output, i.e., the reduced ability of the heart to output oxygenated blood from the left side of the heart, may result from various abnormalities and diseases of the heart. This reduction in output is typically due to aortic valve disease. There are two major categories of aortic heart valve disease: stenosis and regurgitation. Stenosis involves the narrowing of the aortic outflow tract, causing obstruction to blood flowing from the left ventricle into the ascending aorta. As illustrated in FIG. 1A, the stenosis typically involves the buildup of calcified material 2 on the valve leaflets 4, causing them to thicken and impairing their ability to fully open to permit adequate forward blood flow. Stenotic build up 6 may also occur beneath the valve leaflets 8, i.e., subvalvular stenosis, as illustrated in FIG. 1B. Severe calcification can greatly impair proper functioning of the aortic valve wherein blood outflow is obstructed. Regurgitation, on the other hand, is the retrograde leakage of blood back through the heart valve and into the left ventricle during diastole. Both stenosis and regurgitation of the aortic valve decrease cardiac output which can ultimately lead to hypertrophy of the left ventricle wherein the size of the ventricular chamber becomes enlarged, leading to diastolic dysfunction of the left ventricle, i.e., the impaired ability of the left ventricle to adequately fill with blood. Diastolic dysfunction accounts for about 20% to 40% of heart failures.
Surgical treatments are available to treat diastolic dysfunction of the left ventricle or their precursors (e.g., a defective cardiac valve); however, these treatments have their drawbacks. For example, the most common treatment for stenotic aortic valves is the surgical replacement of the diseased valve, which can be very invasive, requiring dissection of the patient's aorta. A particular drawback of conventional aortic valve replacement procedures is that they require the patient to be placed on the heart-lung machine (“on-pump”) wherein the heart is stopped and the surgery is performed through an open chest. Because the success of these procedures can only be determined when the heart is beating, the heart must be closed up and the patient taken off the heart lung machine before verification can be made. If the results are determined to be inadequate, the patient must be put back on cardiopulmonary bypass and the aorta must be reopened. Moreover, the risks and complications associated with open-heart surgery, which involves the use of cardiopulmonary bypass, aortic cross-clamping and cardioplegic arrest, are well known. The most serious risks of cardiopulmonary bypass and aortic cross-clamping are the increase in the likelihood of bleeding and stroke. Also, patients who undergo surgeries using cardiopulmonary bypass often require extended hospital stays and experience lengthy recoveries. Thus, while certain conventional heart surgeries produce beneficial results for many patients, numerous others who might benefit from such surgery are unable or unwilling to undergo the trauma and risks of conventional procedures.
In addition to valve replacement, some patients require reconstruction of the aorta as well due to a variety of factors, e.g., aortic dissection and endocarditis. These valved conduits are integrated and allow the surgeon to fix both the aorta and the valve at the same time. Valved conduits are also used in conjunction with LVAD's (Left Ventricular Assist Devices) to facilitate off loading the heart.
Within recent years, minimally invasive types of procedures for coronary artery bypass surgery have been developed which do not require stopping the patient's heart and the use of cardiopulmonary bypass. While attempts have been made to treat aortic valves off-pump via endovascular procedures, e.g., endovascular balloon valvuloplasty, such procedures may provide only partial and temporary relief for a patient with a stenotic valve. Moreover, the rapid restenosis and high mortality following balloon aortic valvuloplasty have led to virtual abandonment of this procedure.
An endovascular, off-pump approach for treating regurgitant aortic valves has been disclosed (see U.S. Pat. Nos. 3,671,979 and 4,056,854). The procedure involves supplementing the regurgitant valve with a mechanical heart valve placed downstream of the native aortic valve and coronary ostia. The mechanical valve is delivered into the aorta by means of a catheter inserted through the brachial or femoral artery, and is subsequently maintained by a mounting catheter which extends out of the arterial entry site. Due to many complications and drawbacks, this treatment regime is not clinically practiced.
Thus, there is an ongoing need for minimally invasive devices and techniques for treating patients suffering from diastolic dysfunction. As such, it is desirable to provide such a procedure which is relatively simple and is easier to perform than conventional valve replacement procedures and reduces the time and cost of the procedure. Moreover, it is desirable to provide such devices and procedures that obviate the need for cardiopulmonary bypass, can be used on a beating heart, involves endovascular or less invasive surgical techniques, and can be used by surgeons.